The print medium for thermal printing is generally in the form of a roll of sheet material which is paid out beneath a print head by means of a drive roll (or capstan) and which is then cut into lengths to constitute separate sheets (or receipts, etc.).
One of the main drawbacks of that type of apparatus lies in the difficulty of threading the leading end of a roll through the print head and between the blades of the device for cutting the sheet into lengths.
Printers have already been proposed in which the print medium is installed from the side, i.e. after removing a cover that is perpendicular to the axes of the capstan and of the roll so that the medium can be slotted in parallel to said axes.
Printers also exist in which the print head is separated from the capstan so that they are moved apart from each other parallel to the axis of the capstan. The capstan is then secured to a chassis component that pivots on a fixed component carrying the print head. The pivoting cover moves in relatively complex manner in order to avoid rubbing contact between the capstan and the head when they are being brought together or moved apart. The capstan support therefore begins its separation movement substantially perpendicularly to the head and then moves parallel to the head for disengagement purposes once the capstan is no longer in contact with the head.
The present invention seeks to simplify the structure of thermal printers that are capable of being opened in order to facilitate insertion of the strip of paper; it also has the advantage of being simpler to use than existing printers.